Compressor lubricant compositions

Abstract

A lubricant composition for use in a sliding-vane rotary vane compressor has a polyalkyleneglycol base oil component and includes antiwear additives, antioxidants and metal passivators and, optionally, anticorrosion agents and vapour phase anticorrosion agents. The polyalkyleneglycol base oil component is a random copolymer of ethylene oxide (EO) and propylene oxide (PO) having an EO:PO ratio between 3:1 and 1:3, preferably between 1.5:1 and 1:1.5, and having been initiated with a compound having five carbon atoms or less.

1 . A lubricant composition for use in a sliding-vane rotary vane compressor comprising: 
 a) a polyalkyleneglycol base oil component, said polyalkyleneglycol comprising a random copolymer of ethylene oxide (EO) and propylene oxide (PO) having an EO:PO ratio between 3:1 and 1:3 and having been initiated with a compound having five carbon atoms or less;    b) 0.01% to 10% based on total weight of the composition of an antiwear additive;    c) 0.05% to 5% based on total weight the composition of an antioxidant;    d) 0% to 1% based on total weight the composition of a metal passivator;    e) 0% to 2% based on total weight the composition of an anticorrosion agent; and    f) 0% to 2% based on total weight the composition of a vapour phase anticorrosion agent.    
   
   
       2 . A lubricant composition according to  claim 1 , in which the polyalkyleneglycol base oil component has a molecular weight such that the kinematic viscosity of the polyalkyleneglycol is at least 10 cSt, more preferably 12 cSt, at the operating temperatures and pressures of the compressor.  
   
   
       3 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has a kinematic viscosity of at least 10 cSt, more preferably 12 cSt at 100° C.  
   
   
       4 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has an EO:PO ratio between 2:1 and 1:2, more preferably between 1.5:1 and 1:1.5, but especially 1:1.  
   
   
       5 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has been initiated with methanol or butanol.  
   
   
       6 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has a viscosity index of at least 150 and, more especially, at least 200.  
   
   
       7 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has a pour point of less then −10° C. more preferably less than −20° C. and particularly less than −30° C.  
   
   
       8 . A lubricant composition according to  claim 1  or  claim 2 , in which the polyalkyleneglycol base oil component has an acid number of less than 0.2 mgKOH/g.  
   
   
       9 . A lubricant composition according to  claim 1  or  claim 2 , which is substantially free of viscosity improvers.  
   
   
       10 . A lubricant composition according to  claim 1  or  claim 2 , which comprises 0.1% to 5%, more especially 0.5% to 2.5%, based on total weight of the composition of the antiwear additive.  
   
   
       11 . A lubricant composition according to  claim 1  or  claim 2 , in which the antiwear additive is selected from phosphates, phosphites, thiophosphates, thiophosphites, dithiocarbomates, amine phosphates and amine phosphates and mixtures thereof.  
   
   
       12 . A lubricant composition according to  claim 1  or  claim 2 , which comprise 0.5% to 2.5% based on total weight the composition of the antioxidant.  
   
   
       13 . A lubricant composition according to  claim 1 , in which the antioxidant is selected from high temperature antioxidants and low temperature antioxidants and mixtures thereof.  
   
   
       14 . A lubricant composition according to  claim 13 , in which the high temperature antioxidant is selected from ashless aminic antioxidants alkylated phenyl naphthylamine, alkylated diphenyl amine, polymerized hydroxyquinolines, iminodibenzyl or mixtures thereof.  
   
   
       15 . A lubricant composition according to  claim 13 , in which the low temperature antioxidant is selected from gallates, sterically hindered phenolic and diphenolic antioxidant or mixtures thereof.  
   
   
       16 . A lubricant composition according to  claim 1  or  claim 2 , which comprises 0.1% to 0.5% based on total weight the composition of the metal passivator.  
   
   
       17 . A lubricant composition according to  claim 1  or  claim 2 , in which the metal passivator is selected from gallates, imidazole, benzimidazole, pyrazole, benzotriazole, tolutriazole, tolutriazole, 2-methyl benzimidazole, 3,5-dimethyl pyrazole, methylene bis-benzotriazole or mixtures thereof.  
   
   
       18 . A lubricant composition according to  claim 1  or  claim 2 , which comprises 0.1% to 2%, more especially 0.1% to 0.5%, based on total weight the composition of the anticorrosion additive.  
   
   
       19 . A lubricant composition according to  claim 1  or  claim 2 , in which the anticorrosion additive is an ashless anticorrosion additive.  
   
   
       20 . A lubricant composition according to  claim 1  or  claim 2 , in which the anticorrosion additive is selected from amine naphthalene sulphonates, amine phosphates, alkenyl succinic half ester, organic polycarboxylic acids or mixtures thereof.  
   
   
       21 . A lubricant composition according to  claim 1  or  claim 2 , which comprises 0.05% to 2%, more especially 0.1% to 0.5%, based on total weight the composition of the vapour-phase anticorrosion additive.  
   
   
       22 . A lubricant composition according to  claim 1  or  claim 2 , in which the vapour-phase anticorrosion additive is selected from dicarboxylic acids, silicones, siloxanes, silanes, silicates, volatile amines or mixtures thereof.  
   
   
       23 . A lubricant composition according to  claim 1  or  claim 2  which has an acid number of less than 0.5mgKOH/g.  
   
   
       24 . A lubricant composition for use in a sliding-vane rotary vane compressor comprising: 
 a) a polyalkyleneglycol base oil component, said polyalkyleneglycol comprising a random copolymer of ethylene oxide (EO) and propylene oxide (PO) having an EO:PO ratio between 1.5:1 and 1:1.5 and having been initiated by methanol or butanol and having a kinematic viscosity of at least 12 cSt at 100° C.;    b) 0.01% to 10% based on total weight of the composition of an antiwear additive;    c) 0.05% to 5% based on total weight the composition of an antioxidant;    d) 0.1% to 1% based on total weight the composition of a metal passivator,    e) 0% to 2% based on total weight the composition of an anticorrosion agent; and    f) 0% to 2% based on total weight the composition of a vapour phase anticorrosion agent.    
   
   
       25 . The use in a sliding-vane rotary vane compressor of a lubricant composition as defined in  claim 1  or  claim 24 .  
   
   
       26 . A method of lubricating a rotary vane compressor comprises utilising a lubricant composition as defined in  claim 1  or  claim 24 .  
   
   
       27 . A sliding-vane rotary compressor charged with a lubricant composition as defined in  claim 1  or  claim 24.